Inspection for inspecting performance of a device (an object to be inspected) such as a semiconductor wafer, an IC or a module, by inputting an electric signal to the device, has been generally conducted. In case of conducting such inspection of electrical performance of the device, there has been employed a socket for inspection such as an IC socket which is provided with probes for interconnecting wiring terminals on a wiring board on which ends of leads to be connected to an inspection unit are collected and electrode terminals (lead terminals) of the device. In this socket for inspection, as shown in FIG. 6, for example, through holes are formed in a support block 92 for supporting probes 91 which is formed of resin or metal, then, the probes 91 for signals, for power supply, and for grounding are inserted into the through holes, and electrode terminals (lead terminals) 90a of a device 90 to be inspected which is provided on one face side of the socket are electrically connected to wiring terminals of a wiring board (not shown) which is provided on the other face side of the socket thereby to conduct the inspection. A device guide 94 formed with an opening 94a for positioning the device 90 to be inspected is provided on an outer peripheral part of this support block 92 at a side where the device 90 to be inspected is mounted, integrally with the support block 92 or formed as a separate component and fixed with screws or the like which are not shown (for example, refer to JP-A-2004-170182). In FIG. 6, reference numeral 93 designates a retaining plate for securing the probes 91 so as not to escape.
As describe above, the socket for inspection is provided with the device guide 94 having the opening 94a of a size to be conformed with a size of the device 90 to be inspected, in order to exactly position the electrode terminals 90a of the device 90 to be inspected with respect to the probes 91. The IC, for example, has an outer shape of a package formed of resin mold in many cases, and there is set a tolerance of ±0.1 mm, in a size of the outer shape of this package, with respect to the package having 30 mm square, for example. It is generally acceptable when the size of the package may be within this tolerance. However, even though the size is within this tolerance, there is a difference of 0.2 mm between the smallest package and the largest package. The opening 94a of the device guide 94 must be formed further larger, by about 0.05 mm, than the size of the largest package, because such a size that even the largest package can be smoothly received is required. For this reason, in case where the size of the package is the smallest within the tolerance, a width C of the package is smaller by 0.25 mm than a width D of the opening 94a, and a gap of 0.25 mm (D-C) is formed. As the results, there is such possibility that positional deviation of 0.125 mm may occur between a center of the device 90 to be inspected and a center point of the opening 94a of the device guide.
Actually, the electrode terminals (balls or lead terminals) of the device 90 to be inspected too are not always arranged in exact positions with respect to the center point of the package, but respectively deviated, and the probes 91 in the socket too are not always provided in exact positions with respect to the center point of the opening 94a. Therefore, when these deviations are superposed to the worse case, positional deviation may occur between the electrode terminals 90a of the device 90 to be inspected and the probes 91 of the socket for inspection. In some cases, the deviation more than 0.2 mm may occur between the electrode terminals 90a and the probes 91. Provided that a pitch of the electrode terminals is 0.5 mm, for example, when such deviation of 0.2 mm has occurred, there is a problem that tip ends of the probes 91 may be offset from respective centers of the electrode terminals 90a (FIG. 7A), or out of contact (FIGS. 7B and 7C), resulting in bad electrical conduction. In the drawings, there is shown an example in which a pitch p of the electrode terminals 90a is 0.5 mm, a ball of the electrode terminal (FIG. 7A) is φ0.3 mm, and a width of a pad of the electrode terminal 90a (FIGS. 7B and 7C) is 0.3 mm.
In order to solve the above described problem, there has been known such a structure that the device to be inspected, which is not shown, is always pressed with pushers 95 by means of springs 96 from two adjacent edges of the opening 94a having a square shape (a mounting part of the device to be inspected) so as to be urged toward one corner of the mounting part, as shown in a plan view in FIG. 8 showing an example of the socket for inspection. According to such structure, the probes of the sockets for inspection are provided by putting a baseline on the corner toward which the device to be inspected is urged, so that an amount of the deviation can be reduced to a half of the above described amount of the deviation, theoretically.
When intervals between the electrode terminals of the device to be inspected become narrow as described above, there is such a problem that reliable contact between the electrode terminals of the device to be inspected and the probes of the sockets for inspection is unable to be obtained in some cases, due to a gap between the opening in the socket for inspection in which the device to be inspected is disposed and the outer shape of the device to be inspected. This tendency leads to more serious problem, when the pitch of the electrode terminals becomes further smaller to less than 0.4 mm. In this case, the problem of defective contact between the electrode terminals and the probes of the socket for inspection cannot be completely solved, even in the method that the device to be inspected is pressed to the one corner of the socket for inspection, as shown in FIG. 8.
Further, in the structure as shown in FIG. 8, because the device to be inspected is always pressed to the one corner with the pushers 95 provided with the springs 96, there is a problem that the device to be inspected is rubbed and is likely to be electrified with static electricity. Moreover, when the device to be inspected is taken out after the inspection, the device to be inspected must be detached against a pressing force. However, in this case, it is difficult to take out the device to be inspected by vacuum suction which is generally employed. In addition, because the device guide (side wails of the opening 94 in FIG. 8) is scraped and an error in size may occur, there is such a problem that durability is deteriorated, and the device to be inspected is more likely to be electrified with the static electricity.